Abstract

The effect of optical feedback on the intensity‐noise spectrum and the longitudinal‐mode line shape of a 1.55‐μm InGaAsP laser is investigated for reflections arising from the far end of a 7.5‐km‐long fiber. The intensity noise near the relaxation‐oscillation frequency is significantly enhanced by the reflection feedback. Owing to the intercavity coupling, the enhancement is, however, frequency dependent and the noise spectrum exhibits high‐contrast modulations with a period corresponding to the fiber‐cavity longitudinal‐mode separation. A simple rate equation model is used to explain the observed behavior.